Field of the Invention
The present invention relates to substrate processing technology for processing a substrate by supplying a processing solution to the substrate while rotating the substrate. The substrate to be processed includes various substrates such as a semiconductor wafer, a glass substrate for liquid crystal display, a glass substrate for plasma display panel, a substrate for optical disc, a substrate for magnetic disk, a substrate for magneto-optical disk, and a substrate for photomask.
Description of the Background Art
For example, Japanese Patent Application Laid-Open Publication No. 2003-209087 and Japanese Patent Application Laid-Open Publication No. 2005-086181 each disclose, as an apparatus for processing a substrate in the manufacturing process of the substrate, an apparatus including a two-fluid nozzle and a nozzle referred to as a straight nozzle. The two-fluid nozzle is used to mix a processing solution and pressurized gas to generate a jet flow of droplets of the processing solution, and to eject the generated jet flow of droplets onto the substrate. The nozzle referred to as the straight nozzle is used to discharge a continuous flow of the processing solution onto the substrate. These nozzles are integrally scanned with a predetermine distance therebetween along the same path above the substrate to process the substrate.
The substrate processing apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2003-209087 cleans the substrate by vertically discharging a mist of a relatively large amount of cleaning detergent, such as pure water, from the two-fluid nozzle onto the substrate while vertically discharging a continuous flow of a relatively small amount of cleaning detergent from the straight nozzle onto the substrate to wet the surface of the substrate with the cleaning detergent. This suppresses scattering of the mist on the surface of the substrate compared to a case where the mist of the cleaning detergent is discharged onto a dry substrate, and thereby suppresses watermark-like defects caused by attachment of the scattered mist of the cleaning detergent to the substrate. The apparatus further includes a shield between the two-fluid nozzle and the straight nozzle. This enables the apparatus to suppress scattering of the mist of the cleaning detergent caused by interference of the continuous flow of the cleaning detergent with the mist of the cleaning detergent before they reach the surface of the substrate. The apparatus also suppresses scattering of the cleaning detergent on the surface of the substrate by vertically discharging the continuous flow of the cleaning detergent to wet the surface of the substrate to reduce horizontal kinetic energy of the continuous flow discharged onto the substrate.
Japanese Patent Application Laid-Open Publication No. 2003-209087 discloses, as a modification, a substrate processing apparatus that integrally scans the straight nozzle that vertically discharges the continuous flow of the relatively small amount of cleaning detergent onto the substrate, and a two-fluid nozzle that obliquely discharges the mist of the relatively large amount of cleaning detergent onto the substrate wet by the continuous flow. In the modification, an obliquely-extending shield is provided between the straight nozzle and the two-fluid nozzle, and the two-fluid nozzle is mounted on the shield. This enables the apparatus in the modification to suppress scattering of the mist of the cleaning detergent caused by interference of the continuous flow of the cleaning detergent with the mist of the cleaning detergent before they reach the surface of the substrate.
The substrate processing apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2005-086181 vertically discharges a continuous flow of an oxidative processing solution, such as ozonated water, from the straight nozzle onto the substrate, and vertically ejects a jet flow of droplets of an etching solution, such as hydrofluoric acid, from the two-fluid nozzle towards the substrate onto an oxide film formed on the substrate to remove foreign matter on the substrate together with the oxide film. The straight nozzle and the two-fluid nozzle are integrally scanned in the apparatus, and thus a processing time of the substrate can be reduced compared to a case where, after the straight nozzle used to discharge the oxidative processing solution is scanned to oxidize the entire upper surface of the substrate, the two-fluid nozzle used to eject the jet flow of droplets of the etching solution is scanned to etch the entire upper surface of the substrate.
In use of the processing solution, such as the etching solution, for processing the film formed on the substrate by chemical reaction, reactivity of the processing solution is usually high when the processing solution is at a high temperature. In etching, the etching rate can be improved by supplying a large amount of etching solution set at a high temperature so as to have high reactivity to the surface of the substrate to be processed. Bubbles may be formed on the surface of the film by chemical reaction between the etching solution and the film. If bubbles are formed, reaction does not proceed in a portion where the bubbles are formed, generating etching residues. When the etching solution supplied to the substrate is at a high temperature, the number of bubbles is large as reactivity of the etching solution is high. In order to effectively suppress generation of etching residues in etching, it is necessary to move the bubbles by stirring a liquid film formed by the etching solution on the substrate while the liquid film is at a high temperature to suppress retention of the bubbles on the surface of the film.
By using an etching technique of, in a short time after the continuous flow of the etching solution set at a predetermined temperature is discharged onto the substrate, ejecting the jet flow of droplets of the etching solution onto the liquid film to stir the liquid film, the etching rate can be improved, and generation of the etching residues can efficiently be suppressed.
The flow rate of the continuous flow discharged from the straight nozzle is easily increased as gas is not mixed, and the speed of the jet flow of droplets ejected from the two-fluid nozzle is easily increased as high-speed pressurized gas and the processing solution are mixed.
As a technique for achieving the above-mentioned etching technique with the apparatus configuration disclosed in Japanese Patent Application Laid-Open Publication No. 2003-209087 and Japanese Patent Application Laid-Open Publication No. 2005-086181 in which the processing solution is vertically discharged from the straight nozzle and the two-fluid nozzle, a technique of discharging a continuous flow of a large amount of etching solution from the straight nozzle onto the substrate, and ejecting, at a high speed, a jet flow of droplets of the etching solution from the two-fluid nozzle onto the liquid film formed by the continuous flow while reducing the distance between the straight nozzle and the two-fluid nozzle is devised.
When the continuous flow of the large amount of etching solution is discharged from the straight nozzle onto the substrate, however, centrifugal force generated by rotation of the substrate, inertial force caused by scanning of the nozzles, movement of the processing solution downstream in the rotation direction of the substrate, spreading of the continuous flow from a landing point that varies depending on the flow rate of the supplied solution, and the like collectively act in the course of spreading of the discharged continuous flow of the etching solution on the substrate. As a result, a raised liquid film that is thicker than a surrounding liquid film is formed on the substrate. The jet flow of droplets ejected from the two-fluid nozzle at a high speed also receives similar force in the course of spreading from the landing position on the substrate, and forms a raised liquid film that is thicker than a surrounding liquid film. In this condition, when the distance between the nozzles is set so that the landing position of the continuous flow of the etching solution and the landing position of the jet flow of droplets of the etching solution become close to each other to efficiently move many bubbles formed on the surface of the film when the etching solution is at a high temperature, a peripheral portion of a raised liquid film 371 formed by a jet flow 361 of droplets may collide with a peripheral portion of a raised liquid film 372 formed by the continuous flow 362 so as to lie on the peripheral portion of the liquid film 372, as illustrated in FIG. 7. In this case, columnar splashes 370 of the solution having a relatively large volume are generated. The splashes 370 are visible droplets having a volume of approximately 0.5 milliliters to several milliliters, for example. The splashes of the etching solution are attached to an inner wall surface of the apparatus and the like, and fall on the substrate W to cause defects on the substrate W. On the other hand, when the landing position of the jet flow 361 of droplets of the etching solution and the landing position of the continuous flow 362 of the etching solution are extremely separated from each other, the splashes 370 are not generated, but the etching solution is not stirred while the etching solution is set at a high temperature so as to have high reactivity, generating many etching residues.
In a case where the above-mentioned etching technique is achieved with the apparatus configuration disclosed in the modification of Japanese Patent Application Laid-Open Publication No. 2003-209087, when a trench (a trench in a pattern formed on the substrate) 11 is vertically formed in the upper surface of the substrate W, and a film U1 formed on the trench T1 is processed, an etching solution 351 near one side wall of the trench T1 formed in the substrate W is not sufficiently stirred as the jet flow 361 of droplets of the etching solution is obliquely ejected as illustrated in FIG. 15. This results in retention of bubbles 99 near one side wall, generating etching residues.